1. Field of the Invention
The present invention relates to a lens apparatus and a camera, and in particular, to a barrier mechanism provided in front of a lens unit so as to protect an image pickup optical system, and a lens driving mechanism that drives a lens unit in the image pickup optical system. In addition, the present invention is suitable for optical equipment such as cameras for 35-mm and 24-mm films, digital still cameras, and video cameras.
2. Description of Related Art
As a conventional barrier apparatus of a lens shutter camera, an apparatus is proposed in Japanese Patent Application Laid-Open No. H10(1998)-68984. In FIG. 27 (FIG. 1 in this official gazette), a barrier driving ring 506 driving the opening and closing of barrier blades 502 and 503 by rotary operation is energized by a spring 507 in the driving direction where the barrier blades open. Then, when the camera is in an image-taking state, the barrier blades are made to be open by rotating the barrier driving ring 506 by an energizing force of the spring 507.
In addition, when the camera is in a barrel-collapsed state, as shown in FIG. 28 (FIG. 9 in this official gazette), the barrier blades are made to be closed by rotating the barrier driving ring 506 in a predetermined direction since a cam face 510a of a base plate 510 pushes a follower arm 506i on the barrier driving ring 506 with resisting the energizing force of the spring 507.
On the other hand, in a transfer apparatus that moves a plurality of lens units, which constitutes the image pickup optical system, in the direction of an optical axis, it is common to move each lens unit in the direction of the optical axis by driving cams.
In addition, a mechanism of moving one lens unit in the direction of the optical axis across a plurality of cam grooves is proposed in Japanese Patent Application Laid-Open No. 2002-14271.
In FIG. 29, a lens unit 652 moves in the direction of the optical axis from a middle position to a telephoto position by an engaging action between a cam pin 619d on a lens holding member 619 and a cam groove 602k formed in a cam plate 602. In addition, the cam pin 619d disengages from the cam groove 602k in the middle position to a wide-angle position, and moves in the direction of the optical axis with the cam pin 646a according to the engaging action between a cam pin 646a on another driving member 646 and a cam groove 640g on a second differential barrel 640.
Nevertheless, in the barrier apparatus disclosed in the above-described Japanese Patent Application Laid-Open No. H10(1998)-68984, the barrier driving ring 506 malfunctions when a spring force of the spring 507 is insufficient because of breakage of the spring 507 caused by a shock from the outside, or the adhesion of sand or dust. Hence, the barrier blades 502 and 503 may remain in a closing state even if the camera is in an image-taking state.
Here, there is a problem that exposure to a film or an image pickup device such as a CCD is insufficient since it is possible to take a picture even when the barrier blades 502 and 503 are not completely open when the camera is in the image-taking state. In order to solve such a problem, a camera is proposed, the camera that is provided with a detection switch, which detects whether the barrier blades are open or close, in a camera body, and that verifies an open/close state of barrier blades on the basis of the detection result of this detection switch. Nevertheless, cost rises in this case to the extent that the detection switch is installed.
On the other hand, in a lens barrel disclosed in Japanese Patent Application Laid-Open No. 2002-14271, two cam grooves (602k and 640g in FIG. 29) are used so as to move one lens unit, and are switched in between middle and telephoto positions. In this structure, another member (646) that guides the lens unit from a lens-barrel collapse position to a wide-angle position is used so as to accurately put the cam pin (619d) in the cam groove (602k) whose edge is cut. Hence, the number of parts increases.